Is there less blood flow to the legs? Let's learn about the ABI test! (Ankle-Brachial Index - ABI)

Do you experience pain in your legs, especially in your calves, when you walk for a short distance? Does the pain subside when you stop for a while and start walking again? This is not something you should just ignore. It could be a sign that there is a problem with the blood flow to your legs. Today, we are going to talk about a very simple, painless test to find out.

What is the Ankle-Brachial Index (ABI)?

Simply put, the Ankle-Brachial Index (ABI) is a simple, painless test that measures the blood pressure in your ankle and arm. It mainly checks for peripheral artery disease (PAD) , which is a condition in which fatty deposits build up in the arteries that carry blood to your legs, causing them to narrow .

Just as a clogged water pipe slows down the flow of water, so too does the narrowing of the arteries in our legs. The ABI test measures this reduction in blood flow. Your ABI is calculated by dividing your ankle blood pressure by your arm blood pressure.

When should I take an ABI test?

There are several reasons why your doctor may order this test. You may or may not have symptoms.

How do you do this test?

This is a very simple procedure. Usually a nurse performs this test. The blood pressure is measured in specific arteries in your arms and ankles.

This uses a blood pressure cuff, just like a regular blood pressure check. It is wrapped around your arm and ankle, one at a time, and then compressed for a few seconds, gradually releasing air.

The main arteries examined here are:

• The brachial artery in the arms.
• The dorsalis pedis artery or posterior tibial artery is an artery that connects the ankles.

While measuring this pressure, the doctor or nurse also listens to the sound of blood flowing through these arteries using a handheld ultrasound device (Doppler).

This is a noninvasive test, meaning there are no needles or skin incisions. It's just like your regular blood pressure check, except it's done in all four limbs.

How should you prepare before the test?

Follow these steps to get accurate results and make the test easier for you.

• Do not drink anything containing caffeine (coffee, tea, some soft drinks) on the day of the test.
• Do not use tobacco products or alcohol for one hour before the test.
• Do not exercise an hour before the test.
• Wear loose, comfortable clothing that allows you to easily place the pressure cuff on your upper arm and ankle.
• Before going to the test, go to the toilet and empty your bladder.

Also, if you have previously had any surgery to improve blood circulation in your legs, be sure to tell the person doing the test about it.

What happens during the test?

Before the test begins, you will be asked to lie down on a bed and rest for 10 to 30 minutes. You will be asked to lie down with your arms facing up throughout the test. Sometimes, to get the most accurate reading, your hands and ankles may need to be elevated with something like small pillows so that they are at the same level as your heart.

Then, the tester measures the pressure in this order:

1. Blood pressure is measured in one arm.

2. Blood pressure is measured at the ankle of the leg on the same side as the arm.

3. Measure the blood pressure at the ankle of the other leg.

4. Measure the blood pressure in the other arm.

They will tell you if the measurement needs to be repeated. The entire pressure measurement process only takes a short time, between 10 and 20 minutes .

Are there any risks with this test?

The ABI test is a very safe test . There are usually no risks. However, if you have any of the following conditions, you should tell your doctor or examiner in advance:

• If you have open wounds or ulcers on your leg, the pressure cuff will not be placed over that wound. You may need to do another test.
• If you have recently had vascular bypass surgery , it can be dangerous to apply pressure to such an area with a pressure cuff, as there is a risk of blood clots forming.

How to understand the results?

How to calculate ABI value

This is very easy. You take the highest systolic value (that is, the top number of the pressure) from your two ankle pressure readings and divide it by the highest systolic value from your two arm pressure readings.

For example, consider:

• The pressure in your left ankle is 105/65, and in your right ankle it's 100/60.
• The pressure in your left arm is 130/85, and in your right arm it's 125/80.

Now let's take the highest value from the ankle (105) and divide it by the highest value from the hand (130).

105 ÷ 130 = 0.8

Based on this value of 0.8, you can say that you have mild PAD.

Meaning of the results

The ABI value should normally be between 1.0 and 1.3. An ABI value of 0.9 or less indicates that you have PAD.

Sometimes the ABI value can be higher than 1.4 . This means that your arteries are hardened (calcified) due to aging or diabetes. In such cases, the ABI test alone cannot tell for sure whether you have PAD. In that case, your doctor may order another test, such as the toe-brachial index (which measures pressure in the big toe instead of the ankle).

When do you need to talk to your doctor?

If you don't get your results right away, talk to your doctor who ordered the test. Depending on your results, you may need other tests or treatment.

If your ABI is outside the normal range, you may need to repeat this test periodically. This will help your doctor see if your PAD is getting worse or if treatment is working.

ABI test, Ankle-Brachial Index, PAD, peripheral artery disease, leg pain, blood pressure, atherosclerosis